Fish stocks & MPAs Flashcards
Global MPA’s
6,000 MPAs established globally (Chape et al., 2005)
together, they cover an area of approximately 2.85 million km2 (not actually very much), representing:
- 8% of the world’s 361 million km2 of ocean
- 0% of the 147 million km2 of the ocean under national jurisdiction
Of the global marine area that is protected, only 300,000km2 - i.e. just under 10% of the global MPA area - is a marine reserve (‘no-take’ MPA)
Hard to put legislation in place in the high seas
What piece of legislation protects our UK seas?
Marine & Coastal access act (in 2009)
- The Act includes provision changing the system for licensing the carrying on of activities in the marine environment.
- It also provides for the designation of conservation zones.
- It changes the way marine fisheries are managed at a national and a local level and modifies the way licensing, conservation and fisheries rules are enforced.
- It allows for the designation of an Exclusive Economic Zone for the UK, and for the creation of a Welsh Zone in the sea adjacent to Wales.
- The Act also amends the system for managing migratory and freshwater fish and enables recreational access to the English and Welsh coast.
Why is the marine and coastal act important for MPA’s?
Key in the UK context
– fisheries and conservation authorities (replaces sea fisheries committees) – comprehensively concerned with managing inshore waters (12 nautical miles).
Brought in Ifcas? ITCZ?
Big zones are way offshore – inshore areas are far away where there is less competition.
In the context of England the purpose is for biodiversity conservation as a whole – not actually to manage fisheries.
What effects can we expect these areas to have on fish and fisheries?
MPA’s underlying theory for fisheries
We need to have a mechanism for building up biomass of the animals of interest inside the MPA.
MPA – protect the larger fish that would otherwise be removed from fishing
The exponential relationship between egg production and female fish size
Cause overspill of larva (larval export effect) and fish
To demonstrate the net spillover (spillover effect) and larval export a larger amount of tagging would have to be done, whilst being mindful that stocks would be moving in both directions.
(size effect, reproductive effect, and abundance effect)
Spillover effect - movement of sub adults and adults from the MPA.
Why would they move out
- Higher densities - competition. Density dependant effect on movement.
- Predation
Ecosystem bias in the evidence
- Alot of the MPAS that have been set up in the tropics have been set up in and around reefs, and these are where a lot of the information on reefs ah come from.
- Imbalance of studies proportional to the total area they cover – the highest proprtion of studies have been done on reefs which represent under 0.01% of the oceans as a whole.
Spillover concept
But how mobile are target species? And what about larval export effects?
Abesamis RA et al. 2006 Aquatic Conservation
- If the animal remains in the MPA the graph of abundance will show a dramatic decline with distance from the MPA. The more mobile the species (partially migrates, moves around) will show a less steep decline, and a highly mobile species like a tuna will show very little difference.
Apo and Sumilon
- In Sumilon, with time since the MPA was set up there is generally an increase in biomass, something similar is seen in Apo.
- Should expect fisheries benefit – spillover effect.
- Data shows some increase for Sumilon but no increase for Apo.
- An increase in biomass within both MPA’s, but the underlying expectation of the spillover effect is not clear. And forms the basis of a lot of our understanding.
Spillover surgeonfish
(Abesamis and Russ, 2005)
Ecological Applications
Apo Island No-take Marine Reserve in the Philippines. P
- Surgeonfish
- Quite a mobile animal
- Shows spillover effect, but confined to 300 m from the boundary
- Spillover, the net export of adult fish, is one mechanism by which no‐take marine reserves may eventually have a positive influence on adjacent fisheries - no study to date has demonstrated development of the process.
- This study provides evidence consistent with density‐dependent export of a planktivorous reef fish, Naso vlamingii, from a small no‐take reserve (protected for 20 years) at Apo Island, Philippines.
- Mean density of N. vlamingii increased threefold inside the reserve between 1983 and 2003. Density approached an asymptote inside the reserve after 15–20 years of protection. Modal size in the reserve increased from 35 to 45 cm total length (TL) over 20 years of protection. In addition, both density and modal size increased outside the reserve close to (200–300 m), but not farther from (300–500 m), the reserve boundary over the 20 years of reserve protection.
- Movement of adult N. vlamingii across the boundaries of the reserve was rare. Aggressive interactions among adult N. vlamingii were significantly higher (by 3.7 times) inside than outside the reserve.
- This suggests that density‐dependent interactions were more intense inside the reserve.
- When interacting adults differed in size, the larger individual usually chased away the smaller one.
- Furthermore, the mean size of adult fish captured by experimental fishing decreased from 35‐cm TL 50– 100 m outside the boundary, to 32‐cm TL 250–300 m outside the boundary.
- This represents some of the best evidence available for density‐dependent home‐range relocation of fish from a no‐take reserve.
What problem does marine MPAS face that are less of a problem for terrestrial protected areas?
Body mass to home range size ratio, marine species are particularly mobile for there size.
Home range size increases as body mass increases.
Home range size of larger species are at greater spatial scales than the MPAs.
Give some social and ecological negative effects of MPA’s.
- Value decreases
- Fisheries decline
- Low spillover, smaller dishing ground
- Health decreases
- People marginalised, less empowerment
- Tourism decreases
- Biodiversity and ecosystem health declines
Give some social and ecological positive effects of MPA’s.
- Fisheries targets increase beyond NTA boundaries
- Fisheries improve
- Value increases
- Health increases people empowered
- Biodiversity and ecosystem health increases
- Tourism increases
Nick paper on the give some social and ecological negative effects of MPA’s evidence base
Caveen AJ et al. 2012 Environmental Conservation
(Graph)
Know loads about reefy habitats, but very few studies to go on for other environments.
More about hard substrate habitats than soft sediment ones.
The scientific literature (including some of the most high-profile papers) on the ecological and fisheries effects of permanent no-take marine reserves is dominated by examples from hard tropical and warm temperate ecosystems. It appears to have been tacitly assumed that inference from these studies can directly inform expectations of marine reserve effects in cooler temperate and cold temperate waters. Trends in peer-reviewed studies indicate that the empirical basis for this assumption is tenuous because of a relative lack of research effort in cooler seas, and differences between tropical and temperate regions in ecology, seasonality, the nature of fisheries and prevailing governance regimes.
Problems with lengths of studies.
Need to know more about processes - production of larvae and what happens to them etc. Need to know the behaviour of the whole system and the interactions. Studies are often snapshot rather than understanding processes and dynamics.
What are the different challenges faced by different approaches to studying MPA’s?
- Snapshot - suffer from problems of scale - diver surveys not covering enough area
- Experiments - cant do at scale
- Models - challenged by the data, need info on fundamental processes.
- Macroecology - reaching the desired rigour is challenging
- Comparison is attempting to be at large scale
